// Package challenge6 contains the solution for Challenge 6.
package challenge6

import (
	"regexp"
	"strings"
)

// CountWordFrequency takes a string containing multiple words and returns
// a map where each key is a word and the value is the number of times that
// word appears in the string. The comparison is case-insensitive.
//
// Words are defined as sequences of letters and digits.
// All words are converted to lowercase before counting.
// All punctuation, spaces, and other non-alphanumeric characters are ignored.
//
// For example:
// Input: "The quick brown fox jumps over the lazy dog."
// Output: map[string]int{"the": 2, "quick": 1, "brown": 1, "fox": 1, "jumps": 1, "over": 1, "lazy": 1, "dog": 1}
func CountWordFrequency(text string) map[string]int {
	words := make(map[string]int)

	re := regexp.MustCompile(`[^a-zA-Z0-9]+`)

    text = strings.ReplaceAll(text, "'", "")
    text = re.ReplaceAllString(text, " ")
    
    splitted := strings.Split(text, " ")

	for _, v := range splitted {
		
		v = re.ReplaceAllString(v, "")

		word := strings.Trim(strings.ToLower(v), " ")

		if word == "" {
			continue
		}

		count, exists := words[word]
		if exists {
			count++
		} else {
			count = 1
		}
		words[word] = count
	}
    return words
}